Attribute error: 'int' object has no attribute 'step'

[nmimunro]

I am trying to run the Session 11 tutorial. I have copied all the code across and it seems to work fine for each stage of the model until I get to the run stage. I run it using the following commands:

model = SugarscapeG1mt()
model.run_model(step_count=1)

I get a warning message as follows:
0
C:\Users\nmm9b\AppData\Local\Temp\ipykernel_25528\2571079642.py:82: DeprecationWarning: Because of the shift to using AgentSet, in the future this attribute will return a dict withtype as key as AgentSet as value. Future behavior is available via RandomActivationByType._agents_by_type
for sugar in self.schedule.agents_by_type[Sugar].values():

And I get an Attribute error as follows:
{
"name": "AttributeError",
"message": "'int' object has no attribute 'step'",
"stack": "---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
Cell In[94], line 2
1 model = SugarscapeG1mt()
----> 2 model.run_model(step_count=1)

Cell In[89], line 95, in SugarscapeG1mt.run_model(self, step_count)
93 for i in range(step_count):
94 print(i)
---> 95 self.step()

Cell In[89], line 83, in SugarscapeG1mt.step(self)
81 # step Sugar agents
82 for sugar in self.schedule.agents_by_type[Sugar].values():
---> 83 sugar.step()
85 # step Spice agents
86 for spice in self.schedule.agents_by_type[Spice].values():

AttributeError: 'int' object has no attribute 'step'"
}

The Python version I am using is 3.12.1.

What could be the source of these error messages?

[rht]

It means the Mesa version you are using is not the latest version. We did an accidental API change that is not backward-compatible in 2.2.0. Should have been fixed to be backward compatible in 2.2.3 (latest version as of today). cc: @projectmesa/maintainers

[rht]

I can't seem to mention @projectmesa/maintainers. cc: @tpike3 @quaquel @EwoutH.

[nmimunro]

Tried installing latest version of mesa from github using this command:
pip install -U -e git+https://github.com/projectmesa/mesa@main#egg=mesa
...-but still got the same error. What am I doing wrong?

[EwoutH]

81 # step Sugar agents
82 for sugar in self.schedule.agents_by_type[Sugar].values():
---> 83 sugar.step()

Are we (accidentally) returning the agent’s unique_id instead of the Agent object itself?

[rht]

Yes, the current latest main implementation is wrong: https://github.com/projectmesa/mesa/blob/7b0d3f12f0fb2a0f2dc3ec1bcca4a95a82ff6cee/mesa/time.py#L302.

[quaquel]

The 2.1.5 version has

self.agents_by_type[agent_class][agent.unique_id] = agent

So the current code has the key and value swapped the wrong way around.

[rht]

Will be fixed when:

• Revert "fix: Use new API to loop over agents_by_type" mesa/mesa-examples#91 is merged
• fix: Reverse dict key and value for agents_by_type mesa/mesa#1996 is merged
• Mesa 2.2.4 is released, which is very soon after the previous 2 have been merged

[nmimunro]

So I should wait until Mesa 2.2.4 is released? Or should I look for an older version of Mesa which doesn't have the problem?

[rht]

@nmimunro Mesa 2.2.4 has just been released. Would be great if you can confirm that it fixes the problem.

[nmimunro]

Yes, the code seems to be running correctly now, at least for session 11, though I do get some warning messages. Can I ignore these? See below.
C:\backup\research\abmfiles\workspace\mesa_tutorial\src\mesa\mesa\time.py:82: FutureWarning: The AgentSet is experimental. It may be changed or removed in any and all future releases, including patch releases.
We would love to hear what you think about this new feature. If you have any thoughts, share them with us here: mesa/mesa#1919
self._agents: AgentSet = AgentSet(agents, model)
C:\Users\nmm9b\AppData\Local\Temp\ipykernel_10088\1920272918.py:83: DeprecationWarning: Because of the shift to using AgentSet, in the future this attribute will return a dict withtype as key as AgentSet as value. Future behavior is available via RandomActivationByType._agents_by_type
for sugar in self.schedule.agents_by_type[Sugar].values():
C:\Users\nmm9b\AppData\Local\Temp\ipykernel_10088\1920272918.py:87: DeprecationWarning: Because of the shift to using AgentSet, in the future this attribute will return a dict withtype as key as AgentSet as value. Future behavior is available via RandomActivationByType._agents_by_type
for spice in self.schedule.agents_by_type[Spice].values():
C:\Users\nmm9b\AppData\Local\Temp\ipykernel_10088\1920272918.py:93: DeprecationWarning: Because of the shift to using AgentSet, in the future this attribute will return a dict withtype as key as AgentSet as value. Future behavior is available via RandomActivationByType._agents_by_type
trader_shuffle = list(self.schedule.agents_by_type[Trader].values())

[rht]

Yes, you can ignore the warnings. They should be gone by Mesa 2.3.0.